Monitoring cameras are commonly used to monitor building, roads, shops and various other places. In particular, cameras are often used to monitor scenes to allow automatic detection or tracking of events in the form of presence of motion or presence of an object of a specific type. Such monitoring cameras can be used both indoors and outdoors.
Closing in on the context of the present teachings there are camera arrangements consisting of one or more fixedly arranged cameras having a wide field of view and a pan-tilt-zoom camera (PTZ camera) enabling a narrow field of view (with elevated zoom). When using such camera arrangement an operator may use the fixedly arranged cameras as an input for an overview image, and subsequently utilize the PTZ camera to obtain a detailed view of a particular object located in the overview image (i.e., located in the imaged scene). A user may click on a position in an overview image whereby the PTZ camera is moved to the particular position. By defining a position and a size (e.g. by click and drag) the desired pan position, tilt position and zoom setting may be specified already in the overview image. Such a system is disclosed in US Patent Publication No. 2013/0162838.
The operation of a system having the above described functionality would require a translation from coordinates of an overview image (which may comprise views of several cameras) to pan, tilt, and zoom parameters for the PTZ camera. The calibration may be performed automatically or manually, and the result may be a system where information from an overview image, typically acquired by a statically arranged camera, may be used to control a movable camera, typically a PTZ camera. An early disclosure of such a system is found in U.S. Pat. No. 5,434,617.
In an installation where the PTZ camera is automatically guided to an object detected by the overview cameras there may be an issue as soon as a second object enters the overview scene in that some selection would have to be made; e.g. maintain the view of the first object as a default, shift to the second object as a default, or start switching between the two objects as a default.
The present teachings relate to improvements in this technical field, in particular when tracking two or more objects.